The present invention relates to an electron beam test system and an electron beam test method, and particularly relates to an electron beam test system and an electron beam test method able to determine whether a potential is high or low about a signal such as a DC signal or a signal having no potential change before the time of observation.
FIG. 4 shows a conventional electron beam test system.
The electron beam test system 100 has an electron beam prober 101, a high accuracy LSI tester 102 for operating a device connected to this electron beam prober 101, a control engineering work station (EWS) 106 for controlling operations of the electron beam prober 101 and the high accuracy LSI tester 102.
The electron beam prober 101 has a structure constructed such that a beam blanker 103 for forming a pulse beam, an analytical grid 104 for observing potential distribution and measuring a waveform, and a waveform measuring unit 105 connected to this analytical grid 104 are added to a SEM (scanning electron microscopy). A fixed stage 109 for placing a semiconductor wafer is arranged on an X-Y movable stage 108.
A non-defective or defective semiconductor wafer (semiconductor integrated circuit device) is placed on the fixed stage 109.
This semiconductor wafer is connected to a test head 110, and is operated by this test head 110. Concretely, a predetermined test pattern signal including a clock signal is inputted from the test head 110 to each input terminal of the semiconductor wafer.
The operated semiconductor wafer is irradiated with electron beam by a field emission gun (FE-Gun) 107 through the beam blanker 103.
A secondary electron from the semiconductor wafer is detected by a secondary electron detector 111 through the analytical grid 104, and a voltage waveform of the operated semiconductor wafer, etc. are measured by the waveform measuring unit 105.
FIG. 5 shows one example of the test pattern signal supplied to the semiconductor wafer and its measured waveform. Here, one example of a clock signal waveform of wiring of the semiconductor wafer and a differential waveform through a passivation film is shown.
As shown in this figure, the differential waveform is detected through a passivation film in the voltage waveform measurement in the electron beam test system. When a desired test pattern signal is supplied to the semiconductor wafer, a clock period is lengthened and a potential contrast image is obtained.
In the above conventional electron beam test system, the image of a low potential becomes light and the image of a high potential becomes dark in a pulse signal such as a clock signal. Accordingly, the observation can be made similarly to a state having no passivation film even when no passivation film is separated.
However, in the conventional technique, the image becomes gray (intermediate color) with respect to a direct current (DC) signal or a signal having no potential change before the time of observation. Therefore, no high/low potentials can be judged so that it is difficult to recognize the potential.
Further, in the conventional technique, potential contrast is detected every time a desired test pattern signal is inputted while the test pattern signal is looped. In this case, a plurality of shots are required to detect the potential contrast every time the test pattern is looped. The obtained potential contrast data is then integrated, and a final potential contrast image is generated.
Accordingly, in the conventional technique, it takes time to generate a potential contrast image, so that fault or breakdown caused by process defect cannot be rapidly analyzed.
In addition, in such a conventional technique, a defective phenomenon having no repeatability can not be observed.